Industrial boilers, such as oil-fired, coal-fired and trash-fired boilers in power plants used for electricity generation and waste incineration, as well as boilers used in paper manufacturing, oil refining, steel and aluminum smelting and other industrial enterprises, are huge structures that generate tons of ash while operating at very high combustion temperatures. These boilers are generally characterized by an enormous open furnace in a lower section of the boiler housed within walls constructed from heat exchanger tubes that carry pressurized water, which is heated by the furnace. An ash collection and disposal section is typically located below the furnace, which collects and removes the ash for disposal, typically using a hopper to collect the ash and a conveyor or rail car to transport it away for disposal.
Each plant includes a number of cleaning devices known as long retractable sootblowers mounted to the exterior walls of the furnace. The long retractable sootblower includes an extending and retracting lance that enters into the furnace to blow water and/or steam onto the interior of the furnace to remove accumulated ash and slag. The movable lance tube surrounds and moves telescopically along a fixed supply tube, which receives a supply of steam through a control valve. The supply tube is mounted to the exterior of the furnace and a carriage assembly moves the lance tube along the supply tube to extend and retract the lance tube into and out of the furnace. As a telescoping tubular structure, the sootblower is a long and narrow device with the length depending on the particular boiler served by the sootblower and, in many case, the section of the furnace serviced by the particular sootblower.
The sootblower is typically housed within a canopy, which serves as a frame that supports the sootblower and a cover that protect the supply tube and carriage assembly. The canopy is typically bolted to the exterior of the furnace and extends the full length supply tube. The carriage assembly is supported by and travels on a pair of tracks mounted to the inside of the side panels of the canopy. The length of the canopy therefore varies with the length of the associated sootblower. Because the lengths vary, sootblower canopies have conventionally been custom made for their associated sootblowers. As a result, maintenance is costly because spare parts have to be made to order or kept in inventory for each different canopy.
One type of conventional sootblower canopy, known as a closed frame canopy, is formed as a three-sided channel with the top integrally formed with the side panels. This design does not permit removal of the top for maintenance access. Another type of conventional sootblower canopy, known as an open frame canopy, has sidewalls but no top or bottom, permitting maintenance access from above and below the sootblower. It is also known to attach trusses between the side panels and place covers on top of open frame canopies to protect and prevent dust and grime from accumulating on the sootblower.
There have been attempts to address the maintenance and spare parts inventory problems associated with sootblower canopies. Certain prior sootblowers have been made with continuous sidewalls or beams extending seamlessly from the front plate to the rear plate. This design is intended to ease the inventory burden by allowing various lengths of sidewall to be manufactured from common roll stock while achieving acceptable strength and rigidity in the frame. See, for example, Johnston, U.S. Pat. No. 5,299,533 and Gallacher, U.S. Pat. No 5,353,996. Although these solutions reduce the cost of maintaining inventory by making all of the canopy sidewalls from the same roll stock, this solution still requires that spare parts be made to order or kept in inventory for each different length of canopy. Therefore, there remains a need for an improved sootblower canopy system that does not require spare parts made to order or inventoried separately for each length of sootblower.